Various types of cooling apparatuses that employ a coolant in the prior art include cooling water supply apparatuses for supplying cooling water to factories, stores and the like. In such a cooling water supply apparatus, water and the coolant are caused to circulate inside a heat exchanger so that by performing heat exchange between the coolant and the water, cooling water can be obtained.
A heat exchanger employed in such a cooling water supply apparatus normally adopts a structure in which piping is provided inside a drum. Since a chiller unit for cooling the coolant is connected to the drum, the coolant can circulate inside the drum. In addition, the piping is provided in such a manner that water can flow inside and the discharge side of the piping is connected to a path through which cooling water is supplied to a utilizing facility, such as a factory, a store or the like.
Cooling water is created at the cooling water supply apparatus described above in the manner described below. Namely, coolant from the chiller unit is supplied into the drum of the heat exchanger and at the same time, water is supplied into the piping. This places the coolant and the water in contact with each other via the piping, and, as a result, the heat in the water in the piping is drawn out by the coolant around the piping so that the water becomes cold. This cold water is delivered into the supply path and is eventually utilized as cooling water at the utilizing facility.
However, the cooling water supply apparatus described above still poses the problem described below that is yet to be addressed. Namely, since the circulation of water inside the heat exchanger is stopped during, for instance, night time when it is not necessary to supply cooling water to the utilizing facility, which leaves residual water inside the piping, the coolant and the still water remain in contact over a long period of time via the piping. Consequently, the water inside the piping may become frozen, disabling circulation of water when the operation restarts or damaging the piping.
An object of the present invention which has been proposed to eliminate the problem of the prior art discussed above, is to provide a cooling water supply apparatus with which water can be prevented from becoming frozen inside the heat exchanger after water circulation is stopped.